In this project, the combustion conditions in future aero engines were predicted, the pollution levels on the basis of todays technology were assessed and fundamental processes of pollutant formation were investigated. Finally, 3 promising combustion concepts were identified for application in advanced aero engines although they differ in nitrogen oxide reduction potential, development effort and in technological risk involved. In order to assess the likely emissions from future aircraft gas turbines, a database was established containing information on the combustor inlet conditions for 6 different engine categories. To predict the future nitrogen oxide levels which would be generated by current combustor technology at these future conditions, empirical correlations were applied using the input from the combustor inlet conditions database. Based on the combustor entry conditions for future engines, various pollution reduction methods were selected and critically analyzed. A coordinated series of experimental and theoretical studies was carried out to investigate fundamental aspects of combustion.
This involved studies of:
capabilities of laser diagnostics;
influence of primary zone geometry and stoichiometry;
influence of primary zone homogeneity;
smoke production in rich burning primary zones;
optimisation of a small engine premix duct.
3 different promising combustion concepts were identified:
the double annular combustor (DAC);
the lean premixed and prevaporized combustor (LPP);
the rich burn, quick quench and lean burn combustor (RQL). The lowest nitrogen oxide reduction potential was identified with the lean combustion method without premixing in a staged combustor design (DAC). The LLP concept is expected to reduce nitrogen oxide by more than 75%. The major problems deal with autoignition and flashback. The RQL method tends to provide a smaller nitrogen oxide reduction potential and a smaller technical risk than the LPP method.
Objectives and content: The proposed research is aimed at the development and validation of stochastic MonteCarlo models, for finite rate chemical kinetics interacting with turbulent flows, capable of predicting droplet evaporation; mixing; ignition, extinction and flashback; combustion stability; NOX, soot and CO production and emissions. The implementation of these models into the CFD codes in use by Gas Turbine (GT) manufacturers and the demonstration of its improved predictive ability are also addressed in this Basic Research Project. To achieve that, the Project is structured into the following major tasks:
- Chemical kinetics studies on detailed and reduced mechanisms for real fuels containing aromatic and partially oxidized compounds and unsaturated hydrocarbons. Soot formation schemes are also included.
- Numerical simulation of basic combustion phenomena in Turbulent Flows. Flame stabilization, ignition, extinction and flame surface topology, among other things, will be investigated and its physics unveiled. - Modelling the evolution of mixture composition fluctuations including the prediction of a characteristic time for their decay and a new Surface Density Function (SDF) method.
- PDF transport equations implemented within CFD codes will be specialized and applied, both by industries and universities, to laboratory flames and to combustor geometries, including a kerosene-fired 6 bars rig. NO predictions will be carried out. Joint velocity/composition PDF and LES/PDF coupling will be developed and applied to calculate detailed laboratory flames. The use of the PDF methodology to describe the spray motion and evaporation, prior to combustion, will be investigated.
- High-quality detailed measurements for code validation are required to test the CFD predictions against. An exhaustive database including mixing and flame stabilization and extinction experimental results will be generated.
Four industries and five universities from five different EU member states participate in this Project. The economic benefit of acquiring combustion technology, capable of meeting future stringent emission levels without hazard to the air worthiness, is the maintenance of a European aero gas turbine industry. Failure to match or better the USA competitors will result in an inability to compete in future engine sales. Earlier investment in the USA has produced a technology lead in all fields, including CFD, which can only be reduced by collaborative European programmes. The CFD developed as a part of this Project can easily be applied to other industrial sectors, such as, the reciprocating engine and furnace/boiler manufacturers.
Funding SchemeCSC - Cost-sharing contracts
SW7 2AZ London
DE24 8BJ Derby